The proposed research continues studies of the origins, circulation and fate of membranes and of membrane-delimited compartments within frog retinal photoreceptors and other cells of the nervous system. The investigations will be based principally on electron microscopic cytochemistry, immunocytochemistry and autoradiography with supportive fluorescence microscopic, cell fractionation, physiological and biochemical determinations. Most of the work will concern two related facets of membrane circulation: 1. Studies focused on the sorting of membrane proteins to opposite poles of the photoreceptor (the photoreceptive outer segment and the presynaptic terminal) will aim at testing aspects of a model which proposes that sorting begins at the endoplasmic reticulum and continues from distinctive subregions of trans Golgi systems. This work will include studies of the normal functional organization of the Golgi apparatus and will also investigate the impact of agents expected to perturb transport and Golgi functioning in different ways and at different steps. 2. Studies on the cycling and fate of synaptic vesicle membrane in the photoreceptor terminals will concern particularly the influence of weak bases on these processes. (The bases raise intracompartmental pHs in the terminals, and engender the accumulation of structures with the properties of recycling intermediates--relatively large compartments of endocytic origin, which can later give rise to synaptic vesicles.) The details of processes by which recycled synaptic vesicles arise will be investigated. A principal aim will be to determine the involvement of intracompartmental pH and of osmotic phenomena in governing sorting and cycling in the photoreceptor. Participation of lysosome-related bodies in the turnover of synaptic vesicles will also be examined. Collaborative work will continue on identifying genetic mutants with altered peroxisomes. This work is aimed at obtaining material with which to investigate the likelihood that peroxisomes are important in the turnover of membrane components. Disease relatedness: Alterations in membrane cycling and in the turnover of membrane molecules are involved in many disorders affecting the retina and other nervous tissue. (Some of the studies will be directly on cell lines from individuals with such disorders.)